Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$117.40	8.173%	$126.9951	$127.00	$127.00	$127.00
Purchase #2	$225.43	5.617%	$238.0924	$238.09	$238.10	$238.10
Purchase #3	$122.91	6.617%	$131.043	$131.04	$131.05	$131.00
Purchase #4	$97.90	11.770%	$109.4228	$109.42	$109.40	$109.40
Purchase #5	$228.46	11.204%	$254.0567	$254.06	$254.05	$254.10
Purchase #6	$250.89	6.618%	$267.4939	$267.49	$267.50	$267.50
Purchase #7	$14.40	9.689%	$15.7952	$15.80	$15.80	$15.80
7 purchase totals =	$1,057.39		$1,142.8991	$1,142.90	$1,142.90	$1,142.90